Snap action differential actuator



Oct. 8, 1963 R. J. LYNN SNAP ACTION DIFFERENTIAL ACTUATOR 2 Sheets-Sheet1 Filed Dec. 15, 1961 INVENTOR.

ROBERT J. LYNN m- ATTORNEY Oct. 8, 1963 LYNN 3,106,623

SNAP ACTION DIFFERENTIAL ACTUATOR Filed Dec. 15, 1961 2 Sheets-Sheet 2 g5 m I W m 1 51% V w 5 m I co \2 2 m g ;%V v m m 9 8 g a LL 00 m V \A Z A7 3 Ln 0' 1 i E ,6

O A m N Q\ kgr O 00 6 A 8 i INVENTOR.

ROBERT J. LYNN man-0,11

AT TORNEY United States Patent 3,1tl6,623 SNAP ACTlfiN DIFFERENTIALATUATR Robert 3!. Lynn, Morton Grove, ill, assignor to Vapor(Importation, Chicago, ill., a corporation at liclaware Filed Dec. is,961, 9i'- No. 159,715 8 Clai-nis. (Cl. Edd-3) This invention relates ingeneral to a pressure actuator, and more particularly to a snap actiondifferential pres sure actuator for use in operating electrical switchesor wherever there is needed a quick acting thrust force, although otheruses and purposes will be apparent to one skilled in the art.

A particular use of the present invention is in providing pressureactuated electrical switches such as for use in operating an aircompressor or the like. Heretofore, slow acting diaphragm type actuatorshave been employed for use in operating compressors or the like whichhave not been fully satisfactory because of the condition of possiblezero contact pressure.

It is therefore an object new and improved pressure snap action.

Another object of this invention is in the provision of a snap actiondifferential pressure actuator for use in actuating electrical switchesor other devices, wherein positive snap action is provided with nomodulation.

A further object of this invention is in the provision of a snap actiondifferential pressure actuator especially useful for operating snapaction electrical switches, wherein the undesirable condition ofpossible zero contact pressure in switches with slow acting actuators iseliminated.

Other objects, features and advantages of the invention will be apparentfrom the following detailed disclosure, taken in conjunction with theaccompanying sheets of drawings, wherein like reference numerals referto like parts, in which:

FIG. 1 is an axial sectional view taken through a snap actiondifferential actuator according to the invention, and illustrating someparts in elevation for purposes of clarity, and further illustrating theposition of the parts during the time when insuliicient pressure existsto operate the actuator;

FIG. 2 is a fragmentary axial sectional view of the device of FIG. 1 andillustrating the position of the parts when the actuator has been energied or operated by a predetermined pressure;

FIG. 3 is a transverse sectional view taken substantially along line 3-3of FIG. 1;

FIG. 4 is a perspective view of a diaphragm or bellofram used in theactuator of the present invention; and

FIG. 5 is an axial sectional view taken through a modified actuator ofthe present invention.

Referring now to the drawings and particularly to the embodimentdisclosed in FIGS. l3, the snap action differential actuator of thepresent invention includes a sectional housing or casing having a centersection or partition lit), a head section ll secured to one side of thecenter section, and a hollow end section 12; secured to the other sideof the center section. The three sections are substantially cylindricalin shape, although it may be appreciated that they may be of some othershape.

A pair of diaphragms which may be more accurately described asbelloirams, generally designated by the numerals l3 and 14, are securedbetween the engaging housing sections. Each bellofrarn, as shownparticularly in FIG. 4, is bell or hat shaped in its normal shapewherein it includes a cup-shaped center 15 having a conical wall 116 andan end wall 17, and an annular rim or flange 13 extending from the openend of the cup-shaped portion. The belloframs are constructed of asuitable flexible msof this invention to provide a actuator capable ofproviding Z2. terial, such as reinforced rubber or the like, and may befurther provided with a plurality of circumferentially spaced holesthrough which fasteners may extend in se curing the housing sectionstogether. The center section ll) is provided on each end with annularrecesses 19 and ill which respectively serve to receive the annular rimsof the belloframs l3 and id. Mating portions Eli and 22 of the headsection 11 and the hollow end section 12, respectively, are respectivelytelescopically received in the recesses 1& and 26 to firmly grip the rimportions of the belloframs l3 and 14, respectively. A plurality offasteners 23, such as screws, are provided for securing the head sectionill to the center section id while the plurality of screws 24 areprovided to secure the hollow end section l2 to the center section ltl.Thus, the rim portions of the bellofrarns are sandwiched and grippedbetween the adjacent surfaces of the housing sections.

The bellofram i4 is secured at its center to a piston 25 by means of apin 2s. The piston 25 is provided with a bore 2'7 which receives inpress-fit relationship the shank 28 of the pin 2s. The pin also includesa head having an annular flange 2% which overlaps the center of thebellofram and holds it against the end of the piston 25. A circularrecess 3% is provided in the center housing ection to receive the headof the pin 26 and to define with the head of the pin and the bellofram apressure chamber dl. A source of controlling pressure is delivered tothe pressure chamber 31 through a conduit fitting 32 that is threadedlyreceived in a tapped bore 33 in the center housing section in, whichbore intercomrnunicates with an inlet passage 34 that leads to thepressure chamber 31.

The piston 25 is slidably guided in a plastic guide 35 which may beconstructed of nylon, Teflon or the like, and which is provided with abore an extending therethrough which receives the piston. The bore 36merges with an enlarged bore 37 which is in alignment with a bore of thesame diameter in the hollow end section 1.2 and designated by thenumeral 38. It may also be noted that the bore 33 is of the samediameter and in alignment with the recess 3i in the center section it.The plastic guide is secured to the hollow end section 12 by means ofthe screws 24 which also serve to secure the hollow end section 22 tothe center section it The pin 26 in the piston 25 is also provided witha dome-shaped head 39 adjacent the flange 29 which coacts with anannular seat ill defined by one end of a plastic sleeve 41 press-fittedwithin a recess 42 or" the center housing section ill. The plasticsleeve ll. may be constructed of nylon, Teflon, or any other suitablematerial, and includes a central bore 43 of the same size as a centralbore 44 in the center section to define a passageway 45 extendingthrough the center housing section ill The passageway 45intercominunicates the pressure chamber 31 with a second pressurechamber as defined by the bellofram l3 and a recess l7 formed about thecorresponding end of passageway 45.

Normally the bellofram 13 is held in a position as shown in FIG. 1 bymeans of a switch actuating plunger 48 having a bell-shaped head 49 thatmates with a bell or cup-shaped portion of the bellofram. Extending fromthe need is the main body cylindrical in shape and designated by thenumeral Sil which engages a switch plunger 51 of a switch mounted on theend of the head section 111 by means of screws 53. Although the presentinvention is shown in connection with the operation of an electricalswitch, it should be appreciated that other uses and purposes will beapparent to one skilled in the art. The head 49 of the plunger 43 andthe bellshaped portion of the bellofrarn are positioned in a passagewaydefined by a cylindrical recess 54 in the center aroaoas 3 housingsection ill which is of a larger diameter than the recess 47, and acylindrical recess 55 in the head section ill which is of the samediameter as the cylindrical recess 54. A diametrically reducedcylindrical recess 5s extends from the recess 55 and is in axialalignment therewith, and defines with a still further reduced bore 5"! ashoulder 5%. The bore 57 also serves as a guide for the main body 5%? ofthe switch actuating plunger l8. An annular slot is formed in theunderside of the head it? of the switch actuating plunger and identifiedby the numeral 5i, and serves to receive one end of a coil spring 6i),the other end of which is bottomed on the shoulder -53. The coil spring(Al normally maintains the switch actuating plunger and bellofram in theposition as shown in H6. 1, but will be compressed upon a certain amountof pressure being applied against the belloiram from the chamber :6 sothat the switch 52. may be actuated.

When the pressure is below a predetermined amount, the valve between thepressure chambers 3i and 4-6 is closed as shown in HG. l and maintainedin closed position until the pressure within the chamber 3-1 reaches apredetermined amount. The valve or piston '25 is held in the position asshown in FIG. 1 by means of a strong coil spring 61 arranged within thehollow end section 12 and hearing at one end against a sleeve spacer aswhich is maintained in position within the hollow end section 12 bymeans of a cap 63 threaded into the open end of the end section 12. Theother end of the spring fill bears against a flange 64- formed on acup-shaped spring stabilizer 65. An axially extending aperture as isprovided in the stabilizer 65 to receive a diametrically reduced portion67 of the piston 25. The reduced portion 67 defines with the main bodyof the piston a shoulder 63 which receives the stabilizer 55. Theopening or aperture as in the stabilizer 65 is lot a lesser diametricaldimension than the diameter of the main body of the piston 25. Thus, thespring 61 normally maintains a piston 25 in the position as shown inFIG. 1 to close the valve between the chambers 31 and as.

The piston 25 is provided with an axially extending passageway 69therethrough defined by a bore '70 that extends clear through the pin 26and a bore '71 extending from the bore 27 to the other end of thepiston, which serves to dump the air pressure when the pressure withinthe chambers is reduced to a predetermined amount. The pressure isdumped into the hollow end section 12 and out through vents '72 providedin the side wall of the end section. Any number of vents 72, may beprovided in the end section 12. To close the passageway 69 during thetime when mined amount to actuate the switch, a ball check valve '73 isprovided to seat on the end of the bore 71 and to be held in positionthereon by an axially extending and adjustable stop 74 which isthreadedly received in the cap 63 and locked in position by means of alocking nut 75. The ball check valve 73 is held from moving laterallyout of position on the end of the bore '71 by means of a recess 76 inthe end of the piston 25 within which the ball check valve is received.The general operation of the actuator, wherein the snap action isaccomplished results from the pressure reaching a predetermined limitand causing the valve between the pressure chambers 31 and 46 to open byforcing the piston 25 toward the right against the spring 61. Thisaction of the piston closes the end of the passageway 69 by forcing theball check valve '73 against the end of the bore 71 and substantially atthe same time forces the switch actuating plunger 43 toward the left toactuate the switch 52. The switch actuating plunger 48 remains in itsextended position until the air in the chamber 4-6 is suddenly releasedto atmosphere, and at that time the switch actuating plunger 48 snapsback to its original position thereby giving a snap action in bothdirections.

More specifically, the snap action differential pressure actuator of thepresent invention will operate on any the pressure reaches a predeter- 7l differential pressure and as an example on a differential of 10 poundsper square inch. To further exemplify the operation of the actuator,assuming that it is constructed for operation within certain limits suchas to operate the switch when a pressure of 160 psi. is obtained and todeactuate the switch when pressure of p.s.i. is reached. it should beappreciated that these pressure figures may be changed for whatever difierential and pressure values desired, these values being governed by theseat area of the valve between the pressure chambers 31 and as, theeffective area across the bellofram 14, when the piston is in openposition, and the constant of spring oil. When the pressure within thechamber 31 reaches p.s.i., this pressure acting on the exposed area ofthe bellofram id will force the piston 25 to the right by overcoming thebiasing effect of the spring dd. As the piston 25 moves to the right,the rather small but significant area of the seat 39 (the area nowexposed by the unseating of the piston) will also be exposed to the 160p.s.i. pressure and the added force will assist in driving the piston 25to its extreme position thereby seating the ball check valve 73 againstthe end of the bore 71 to prevent air from leaking through thepassageway 69'. Actually, the end of the piston adiacent the ball checkvalve 7 3 bottoms against the ball to close the passageway 6-9 by meansof the ball hitting the stop '74. Thus, the ball check valve iscontrolled by movement of the piston '25. At the time that thepassageway 45 is opened by movement of the piston 25, the pressure willthen operate against the exposed area of the hello-tram 13 in thechamber 46 to overcome the biasing of t is spring 69 and drive theswitch actuating plunger d? to the left against the switch plunger 51 tooperate the switch 52. As the bellofram l3 and switch actuating plunger43 move to the left, a larger area of the bellofram, as limited new onlyby the recess 54, will be exposed to the working pressure. Thus, as theoperating pressure diminishes through the range of the differential, 10p.s.i., the switch actuating plunger 48 will be held in the position asshown in FIG. 2 and the other parts will also assume the positions asshown in FIG. 2.

As the differential pressure is traversed, and the operating pressureapproaches the lower limit of 150 p.s.i., the piston 25 will start tomove back to the left as urged by the spring at. Movement of the piston25 in this direction allows the ball check valve '73 to unseat from theend of the bore "7i. and open the passageway 69 from the pressurechambers 31 and 46 to the atmosphere. The pressure is then dumped to theatmosphere permitting the piston 25 to reseat and thereby permit thebellofram l3 and switch actuating plunger 48 to snap back under theinfluence of the spring 64 and deactuate the switch 52. The actuator isthen prepared to repeat this cycle.

Once the piston 25 is seated, it does not unseat again until thepressure increases by the differential of 10 p.s.i. or in the examplegiven to 160 p.s.i. after which the above sequence is repeated again.And of course, the piston therefore, would not move again toward theleft to the seated position until the pressure drops to 150 p.s.i. orthe differential of 10 psi The operating range of the actuator may bevaried by adjustment of the stop '74 in the cap 63, within certainpredetermined limits.

A modification of the invention is shown in FIG. 5 which only differsfrom the embodiment of FIGS. 1-3 in structural details. Actually, theoperation of this embodiment is substantially identical to that of theembodiment above escribed. Like numerals will be applied to like parts,and only the differences in structure will be pointed out.

The housing sections iii, ill and 12 are substantially identical to thehousing sections in PEG. 1 with the exception that they do not havetelescoping mating portions and in other small details. It may be notedthat the switch actuating plunger 43 protrudes from the end of the headsection 11 in this embodiment, while it is wholly received within thehead section 11 in FIG. 1. Because the plunger does protrude from thehead section 11, spacers 80 are provided between the switch 52 and thehead section around the fasteners 53 to properly space the switch andits plunger 51 relative to the switch actuating plunger 48.

One other major difference is in the construction of the piston 25 whichin this embodiment includes an elongated cylindrically stepped memberhaving large and small diametrical sections 81 and 82 defining ashoulder 83. The smaller section 82 extends through the aperture 66 ofthe spring stabilizer 65, and the shoulder 83 bears against the innerside of the stabilizer. The closure cap in this embodiment differs andmay therefore be designated by the numeral 84 and is provided at itsinterior side with a guide bushing 85 having a guide bore 36 forreceiving in guiding relationship the smaller diametrical section 820ithe piston 25. A recess 87 is provided in the cap 84 against which theball check valve 73 bottoms during closing of the passageway 69extending to the piston 25. Ports 88 extend through the bushing 85 forpurposes of permitting the air to be dumped through the passageway 69and out through the vents 72 during the deactuating of the actuator. Thebushing 85 may be secured to the cap 84 in any desired manner such asbeing in press-fitted relationship therewith.

Gne other difference lies in the pin 26 at the valve end of the piston25. This pin is provided with a threaded body 59 which is threadedlyreceived in the end of the piston 25, and a head 9%) for securing thebellofram M on the end of the piston, and for also providing a conicallyshaped valve seat 91 for seating against the corresponding end of thebore 44 that defines the passageway 45 between the pressure chambers 31and 46. Like the pin 26 in the first embodiment, this pin also isprovided with a bore extending therethrough and identified by thenumeral )2 for connecting to the air pressure dumping passageway 69. Asexplained above, the operation of this actuator is identical to theoperation of the actuator disclosed in FIGS. 1-3 and as alreadyexplained.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention, but it is understood that this application is to be limitedonly by the scope of the appended claims.

The invention is hereby claimed as follows:

1. A snap action differential pressure actuator comprising a casing,first and second spaced pressure chambers in said casing, means forsupplying a pressure to said first pressure chamber, means forintercommunicating said chambers, first and second belloframsrespectively responsive to the pressures in said first and secondpressure chambers, valve means operable by said first bellofram toselectively open and close said intercommunicating means in response toa predetermined pressure in said first chamber, an actuator'operable bysaid second bellofram in response to a predetermined pressure in saidsecond chamber, and means for normally maintaining said predeterminedpressure when said valve means is in open position and for dumping thepressure in said second chamber to atmosphere when said valve means isin closed position.

2. A snap action differential pressure actuator comprising a casing,first and second spaced pressure chambers in said casing, means forsupplying a pressure to said first pressure chamber, means forintercommunicating said chambers, first and second belloframsrespectively responsive to the pressures in said first and secondpressure chambers, valve means operable by said first bellofram toselectively open and close said intercommunicating means in response toa predetermined pressure in said first chamber, spring means actingagainst said valve means to continually urge it into closed position, anactuator engaging said second bellofram and driven in one directionthereby in response to a predetermined pressure in said second chamber,spring means for driving said actuator in the opposite direction in theabsence of said pressure in said second chamber, and means for normallymaintaining said predetermined pressure when said valve means is in openposition and for dumping the pressure in said second chamber toatmosphere when said valve means is in closed position.

3. A snap action differential pressure actuator comprising a casing,first and second spaced pressure chambers in said casing, means forsupplying a pressure to said first pressure chamber, means forinter-communicating said chambers, first and second belloframsrespectively responsive to the pressures in said first and secondpressure chambers, valve means operable by said first bellofram toselectively open and close said intercommunicating means in response toa predetermined pressure in said first chamber, means operable by saidvalve means for intercornrnunicating said second pressure chamber withthe atmosphere when said valve means is in closed position to dump thepressure from said second pressure chamber and for closing communicationbetween said second pressure chamber and atmosphere when said valvemeans is in open position, and an actuator operable by said secondbellofram in response to a predetermined pressure in said secondchamber.

4. A snap action differential pressure actuator comprising a casing,first and second spaced pressure chambers in said casing, means forsupplying a pressure to said first pressure chamber, means forintercommunicat-ing said chambers, first and second belloiframsrespectively responsive to the pressures in said first and secondpressure chambers, valve means operable by said first bellofra-m toselectively open and close said in-tercommunicating means in response toa predetermined pressure in said first chamber, means operable by saidvalve means for intercommunicating said second pressure chamber with theatmosphere when said valve means is in closed position to dump thepressure from said second pressure chamber and for closing communicationbetween said second pressure chamber and atmosphere when said valvemeans is in open position, spring means acting against said valve meansto continually urge it into closed position, an actuator engaging saidsecond bellofram and driven in one direction thereby in response to apredetermined pressure in said second chamber, and spring means fordriving said actuator in the opposite direction in the absence of saidpressure in said second chamber.

5. A snap action differential pressure actuator com prising a casing,first and second spaced pressure chambers in said casing, means :forsupplying a pressure to said first pressure chamber, means forinterconrmunicating said chambers, first and second belloframsrespectively responsive to the pressures in said first and secondpressure chambers, valve means operable by said first bellofram toselectively open and close said inter-communicating means in response toa predetermined pressure in said firs-t chamber, ball check valve meansoperable by said valve means into closed position when said valve meansis in open position and for intercommunicatin-g said second pressurechamber with the atmosphere when said valve means is in closed positionto dump the pressure from said second pressure chamber, an actuatorengaging said second bellofram and driven in one direction thereby inresponse to a predetermined pressure in said second chamber, and springmeans for driving said actuator in the opposite direotion in the absenceof said pressure in said second chamber.

6. In combination with an electric switch, a snap action difierentialpressure actuator for operating said switch, said snap actiondifferential pressure actuator comprising a casing, first and secondspaced pressure chambers in said casing, means connecting said firstchamber with a source of variable pressure, passage meansinter-communicating said chambers, first and second bellofra msrespectively responsive to predetermined pressures in said first andsecond pressure chambers, valve means operable by said first bellotramto selectively open and close said passage means in response to apredetermined pressure in said first chamber, means operable by saidvalve means for intercommunicating said second pressure chamber with theatmosphere when said valve means is in closed position to dump thepressure from said second pressure chambers and for closingcommunication between said second pressure chamber and atmosphere whensaid valve means is in open position, spring means acting against saidvalve means to continually urge it into closed position, an actuatorengaging said second bellofram and driven in one direction thereby inresponse to a predetermined pressure in said second chamber, saidactuator couple to said electric switch for controlling same, and springmeans for driving said actuator in the opposite direction in the absenceof said pressure in said second chamber.

7. in combination with an electric switch, a snap action differentialpressure actuator for operating said switch, aid snap actiondifferential pressure actuator comprising a casing, first and secondspaced pressure chambers in said casing, means connecting said firstchamber with a source of variable pressure, passage meansintercommunicating said chambers, first and second beiloframsrespectively re sponsive to predetermined pressures in said first andsecand pressure chambers, first valve means operable by said firstbellofram to selectively open and close said passage means in responseto a predetermined pressure in said first chamber, second valve meansoperable by said first valve means for intercommunicating said secondpressure chamber with the atmosphere when said first valve means is inclosed position for dumping the pressure from said second pressurechamber and for closing communication between said second pressurechamber and atmosphere when said first valve means is in open position,an actuator engaging said second bellofram and driven in one directionthereby in response to a predetermined pressure in said second chamber,said actuator coupled to said electric switch for controlling same, andspring means for driving said actuator in the opposite direction in theabsence of said pressure in said second chamber.

8. A snap action difierential pressure actuator comprising a pair ofspaced diaphragms, a partition extending between said diaphragrnsthereby defining a pair of pressure chambers, an aperture in saidpartition intercommunieating said chambers, one of said diaphragmsacting against a spring biased plunger and the other of said diaphragmsbeing secured to a piston, spring means normally biasing piston againstone end of said aperture thereby sealing the chambers from each other,means for supplying pressure to said chamber having the diaphragmsecured to the piston whereby a predetermined pressure acts against saiddiaphragm to unseat the piston and operates to drive said diaphragmagainst said spring biased plunger to displace same, and means fornormally maintaining said predetermined pressure and for dumping thepressure when it decreases a predetermined amount to permit the pistonto reseat and the plunger to return to its normal position.

References (lited in the file of this patent UNITED STATES PATENTS2,326,763 Trautman June 1, 1943 2,487,418 Birkemcier et a1 Nov. 8, 19492,659,381 Seljos Nov. 17, 1953 2,786,109 Esken Mar. 19, 1957 2,959,352Cunningham Nov. 8, 1960

1. A SNAP ACTION DIFFERENTIAL PRESSURE ACTUATOR COMPRISING A CASING, FIRST AND SECOND SPACED PRESSURE CHAMBERS IN SAID CASING, MEANS FOR SUPPLYING A PRESSURE TO SAID FIRST PRESSURE CHAMBER, MEANS FOR INTERCOMMUNICATING SAID CHAMBERS, FIRST AND SECOND BELLOFRAMS RESPECTIVELY RESPONSIVE TO THE PRESSURES IN SAID FIRST AND SECOND PRESSURE CHAMBERS, VALVE MEANS OPERABLE BY SAID FIRST BELLOFRAM TO SELECTIVELY OPEN AND CLOSE SAID INTERCOMMUNICATING MEANS IN RESPONSE TO A PREDETERMINED PRESSURE IN SAID FIRST CHAMBER, AN ACTUATOR OPERABLE BY SAID SECOND BELLOFRAM IN RESPONSE TO A PREDETERMINED PRESSURE IN SAID SECOND CHAMBER, AND MEANS FOR NORMALLY MAINTAINING SAID PREDETERMINED PRESSURE WHEN SAID VALVE MEANS IS IN OPEN POSITION AND FOR DUMPING THE PRESSURE IN SAID SECOND CHAMBER TO ATMOSPHERE WHEN SAID VALVE MEANS IS IN CLOSED POSITION. 